Conventionally, sink strainers for garbage disposal unit are various in structure. A sink usually has two straining holes one for mounting with a garbage disposal unit, and the other for drainage only, wherein the former hole needs a plug as a stopper and the latter uses a strainer. However, using the plug still encounters setbacks such as when pulling off the plug, spoons or forks will drop into the garbage disposal unit causing damage thereto. Therefore, stoppers having also a function of strainer were developed. One of the examples may be found in U.S. Pat. No. 5,265,281 which discloses a stopper for garbage disposal unit inlets. The prior stopper comprises a side wall defining a bore and carrying an external sealing member for releasably engaging the inner face of the bore of an existing sink flange, an upper flange extending radially outwardly from an upper end of the side wall for covering the upper face of the existing sink flange, a strainer member extending across the bore and a lower wall extending across the bore below the strainer member and including a plug member movable between a sealing position and an open position in which fluid may drain through the stopper. A plug operating member extends upwardly from the plug member and through the strainer member to allow the plug member to be lifted to the open position.
In this prior art, it is necessary to take the whole unit out in order to introduce garbage into the disposal unit. Obviously, such operation is inconvenient.